Method of and a machine for writing



June 9, 1964 E. AscoLl METHOD OF AND A MACHINE FOR WRITING Filed April 9, 1962 4 Sheets-Sheet 1 A L ML* ne. f a \\l'\ 'J Fla. 2 a \\ll\\i f 3H :175 ,o l lp I ,o l P ,P P f2; h' 21 l .\"f Y 24%# 315# 4l# l l l l l I l l/v v l *Vf 2' [Hf l FIG. 7 L 30,@ m =42 /m/f/yrol ENZO SCOL/ @f fi-11E' June 9, 1964 E. AscoLl METHOD OF AND A MACHINE FOR WRITING -4 Sheets-Sheet 2 Filed April 9, 1962 June 9, 1964 E. ASCOLI 3,136,594

METHOD OF AND A MACHINE FOR WRITING June 9, 1964 ASCOM 3,136,594

METHOD OF AND A MACHINE FOR WRITING Filed April 9, 1962 4 Sheets-Sheet 4 f M? f3 54 zr z2; 2,21 *l zzf zz; 2.25 was MM 3,54 M 3,54 MM I 117201193' (20w) 3i (2007s) #(m United States Patent O METHOD F AND A MACHINE FOR WRITING Enzo Ascoli, Lausanne, Vaud, Switzerland, assigner to Paillard S.A., Sainte-Croix, Switzerland, a corporation of Switzerland Filed Apr. 9, 1962, Ser. No. 186,118 f Claims priority, application Switzerland Apr. 14, 1961 v 8 Claims. (Cl. 346--1) This invention relates to a method of and a machine for writing.

Applicant has already proposed writing characters or indicia with the aid of a writing head emitting a jet of ink which is deected by electrostatic tields.

The means previously disclosed by applicant makes it possible to write any character or indicium by producing variations in the electric potentials applied between the deflecting electrodes of the writing fluid emitter in accordance with the components x and y of the outline of the character. It has also been shown that this method enables quick and noiseless writing, faithful response, and is functionally comparable to a tracing on the screen of a cathodic oscillograph.

There has also been previously mentioned the possibility of a continuous relative displacement between the writing fluid emitter and paperduring the writing of a character, with the potentials applied to the deiiection electrodes being modulated to take this displacement into account, but the means for accomplishing this have not been disclosed. It is indeed of the greatest interest to be able to write during relative displacement between the writing lluid emitter and the paper since the time required for this displacement is entirely gained as a new character can be written immediately after the previous character has been written. The following three cases may be considered: f

(a) When the writing is carried out character by character (keyboard) as in a type-writer with a possible intermittence between one character or indicia and the next following character. If, for example, the time taken to write one character is 25 milliseconds, and the time for moving the type-head and the paper relatively to one another is also 25 milliseconds, the minimum `time required to write a character would be 50 milliseconds, i.e. a speed of 20 characters per second, whereas if the relative movement were to take place simultaneously with the writing, the possible maximum speed could be doubled, i.e. 40 characters per second.` Throughout the following specification the abbreviation ms. is used as a designation for millisecond.

`(b) When writing is carried out continuously, for example under the control of a perforated or magnetic tape. In this case, there is no possible intermittence between characters and the effective speed, on the basis of the above values, is doubled. i

(c) When Writing is carried out by a plurality of writing fluids emitters aligned for simultaneous writing and controlled by electronic ordination memorized on tape. In this case, continuity can be assured not only during writing of a line (this applies both to the forwardvand return travel), but also during transfer from one line to the next. f l i An object of the present invention is to enable easy writing during continuous relative displacement between a writing head and the surface which is to be written on. l

Another object of the present invention, is to provide a method of writing on a recording surface whichconsists in, discharging from a nozzle a'jet of writing medium carrying electric charges across an atmospheric gap between the mouth of the nozzle and said surface, controlling the directional movement of the jet to trace characters on said surface by tirst electric potentials with respect to 3,136,594 Patented June 9, 1964 ice at least two coordinated axes substantially parallel to the recording surface, effecting continuous relative movement between said nozzle and said recording surface, and simultaneously correcting the directional movement of the jet by second electric potentials whose values represent at each instant the components, with respect to saidy axes, of the continuous relative movement between said surface and said nozzle whereby the characters may be traced Without deformation despite said continuous relative movement.

A further object of the present invention, is to provide a construction of ywriting machine comprisingr a platen for supporting a recording surface, a writing medium discharge nozzle directed towards said platen and spaced therefrom to form an atmospheric gap between the recording surface and the mouth of said nozzle, means for establishing an electric potential difference between the nozzle and the platen to thereby produce, during operation, a jet of writing Huid from said nozzle to said recording surface across said atmospheric gap, electric potential means for controlling the directional movement of said jet with respect to at least two coordinated axes substantially parallel to the recording surface to trace characters on said recording surface, means for effecting continuous relative movement between said nozzle and said platen, and means for producing electric potentials whose values represent aty each instant the components, with respect to said axes, of said continuous relative movement thereby simultaneously to correct, during operation, the directional movement ofthe jet whereby the characters may be traced without deformation despite said continuous relative movement.

For a better understanding of the invention and to short how the same may be 'carried into effect, reference will now be made to the accompanying diagrammatic drawings, in which:

FIGURES l and 2 are diagrammatic graphic plots illustrating electrical potentials which are useful in some examples for carrying out the method accordinglto the present invention;

FIGURE 3 is a schematic, foreshortened, front elevational view of a portion of a machineaccording to the present invention;

FIGURE 4 is a cross-sectional View taken substantially ony the line IV--IV of FIGURE 3;

FIGURE 5 isi a graphic illustration of several electrical potentials used in theapparatus shown in FIGURES 3 and 4; and

FIGURES 6 and 7 are time and motion explanatory diagrams for the method and apparatus of the invention.

`In a first constructional form or embodiment for carrying out the method of the invention, it will be assumed that we are yconcerned with a form of writing having a constant pitch and with a writing head which travels at a constant speed from the beginning to the end of the line of writing, in parallel relationship to the top and bottom edges of the sheet of paper. Thus:

s=tl1e sensitivity of the writing head in mm./volts,

p=thc constant pitch of the writing in mm. (millimeters),

fzthe frequency in c./s.,

a=the constant amplitude of a periodic potential vx causing a horizontal deflection of the writing head tracing, in volts, and

v=the constant translationary speed of the wiring head in mm./sec.,

vx and vy represent the horizontal and vertical component potentials of the stationary tracing in relation to the writ-y ing head.

Since the relative speedof the movement between the surface being written on and the Writing head is constant, the variation of the movement which takes place is linear E and the potential vx therefore also varies linearly. At each change o-f letter or character, this potential must undergo a constant jump in potential, since the pitch is constant.

The potential vx' will therefore have a saw-toothedlike appearance, as shown in FIGURE l, which satisfies the following equations:

T= sec. a= volts v=pf mm./sec.

This potential vx' is to be added to the component vx of the tracing. T is the time available for writing a character and must be equal to, or be an integral multiple of, the longest time required to trace out a character in order that the tracing may be gone over once or a whole number of times.

The method described above enables the continuous Writing or repetition of the same character if the potentials vx and vy, which represent the horizontal and vertical components of the character to be traced out, are permanently applied during displacement of the Writing head at constant speed along the line being written.

The same method makes it possible to produce any kind of continuous writing if an electronic commutation, which is synchronized with each jump in potential vx (time T1, T 2, T3 and which is, for example, controlled by a memory, e.g. a perforated or magnetic tape, brings about the substitution of the vx and vy potentials which are representative of one character, with the vx and vy potentials of the next following character, and so forth.

The above example may be put into concrete form by a tested numerical example.

s=7.5 X104 mur/volts p=2.5 mm.

f=25 c./s.

a=333 volts v=65.5 mm./sec.

Complete lines composed of any kind of character or indicia were obtained continuously, the frequency of vx and vy being 50 c./s., so that each tracing was gone over twice.

In the preceding example, the speed of movement of the writing head was constant. This condition appears to be desirable for the continuous writing of a whole line, for the time .taken or the distance travelled to bring about the constant speed is negligible in relation to the total time taken to travel the whole line. The extreme lightness of the writing head, which is of the order of 5 grams, is also taken into account. But this condition of constant speed does not appear to be desirable when writing step by step during displacement of the writing head; for example in the case of a key-board operated type-writer for which the ideal displacement law is obviously sinusoidal. The potential vx will therefore have the appearance shown in FIGURE 2.

By analogy, all the remaining considerations relating to the rst example remain Valid.

Generally, displacement may obey any law, provided that the variation in potential vx' be identical. This may be the case when it is difcult to ascertain or apply the law of displacement, for example because of friction or of flexions. In this case, it seems appropriate to read the displacements by means of a suitable transducer which determines the law of variation of the potential vx. The jumps in potential will then be supplied by adding thereto rectangular signals of appropriate value and frequency.

. In a very important application, the method according to the invention may be used for writing at great speed the results issuing from an electronic ordinator.

In the following description, the control means, although necessary for the operation, have been omitted since they are known to specialists in the ield of electronic ordination and, in particular, in the ordination of signals issuing from ordinators for use by existing highspeedprinting means. As is known, at least one line of writing is entirely memorized at a time before being fed into the printing means and by suitable ordination several letters or characters of a line can be printed simultaneously, at the right place and at the right moment.

The main external characteristics of the highspeed printing means which will now be described are as follows:

(l) SPEED AND CAPACITY 750 lines per minute, or 12.5 lines per second; lines of characters each; pitch of 2.5 mm.; length of each line of writing 300 mm.; 4 mm. line spacing; constant and continuous forward movement of the paper at the rate of 50 mm./sec. or 3 m./min.

(2) MISCELLANEOUS The printing means occupies a space smaller than that occupied by a normal oiiice type-writer (approximately half), exclusive of the paper roll.

The operation of the printing means is silent, the only mechanical movements being the continuous unrolling of the paper at a relatively low constant speed (50 mm./ sec.) and the sinusoidal oscillation at a frequency of 375 cycles/min. or 6.25 cycles/sec. of a mass weighing approximately gr. with a total amplitude of l0 mm.

The tracing of the characters or indicia may have any kind of outline and need not be stylized or coded.

The line of writing always remains visible.

In FIGURES 3 and 4, thirty Writing heads represented schematically at El, E2 E1 E30 are mounted on an insulator supporting bar 1, and each head comprises a nozzle 2 (FIGURE 4) and four deflecting electrodes 3. All of the tubes 4 communicate with a single ilexible tube 6 in which they are fitted in a iiuid-tight manner. The conduit 5 in tube 6 is connected by a iiexible tube 7 to a writing fluid or ink reservoir 8 in which the ink at a given level creates a hydrostatic pressure h at the nozzles 2. This pressure is so adjusted in relation to the surface tension of the ink at the nozzle mouth that the ink is prevented from flowing freely out of the nozzle in the absence of an electrostatic eld.

The axes of the thirty writing heads have a spacing of 10 mm. The bar 1 is rigidly secured at each of its ends to one end of a spring blade 9 whose other end is rigidly fixed to the frame A which is not represented in full. Each electrode 3 of each head E is electrically connected by means of a short length of flexible conductor 10 to a terminal carried by a fixed terminal plate (not shown) i.e. 120 terminals, in all. The output of the ordinator control means, to which is subjected the memory of each function vx and vy of each character, also terminates at the terminal plate. The ink is raised to a suitable potential for emission, in relation to a metallic cylindrical platen 11 which is driven to move the paper forward at the rate of 50 mm./sec.

The platen is grounded. Paper feed and take up rollers are also provided, but are not shown as they are conventional in the art. A connecting member, consisting of a spring blade 13, is actuated by an eccentric 14 driven by a shaft 15. This eccentric imparts to the bar 1 a sinusoidal movement having a total amplitude equal to the spacing between the axes of the writing heads, i.e. 10 mm. The shaft 15 which rotates at 375 r.p.m. or 6.25 r.p.s. (i.e. w=12.5 1r rad./sec.), may for example be driven by a synchronous motor M having eight pairs of poles and operating at 50 c./s. The shaft 15 carries a helicoidal pinion 16 which cooperates With a helicoidal wheel 17 fixed to the shaft of cylinder 11 and drives the latter at a speed of 21.4 r.p.m. or 0.357 r.p.s., the transmission ratio being l7.5 l, so that the paper can be moved on a cylinder having a diameter of 44.5 mm. at a linear speed of 50 mm./ sec.; since the spacing between the lines is of 4 mm., 12.5 lines/second or 750 lines/min. are covered as a result of the advance of the paper. As will be seen below, each writing head emits a character in 20 ms. which amounts to 50 characters/sec. and emits four characters per line, successively, with no dead pauses and with a spacing of 2.5 mm. between characters, so that the total time required to Write one line is 4 20 ms.=80 ms., i.e. 1/12.5 sec. and since there are thirty Writing heads,`each.line comprises 30 4=120 characters.

The oscillatory movement of the bar is practically sinusoidal and is represented by curve A in FIGURE 5. Maximum acceleration occurs at the dead points, i.e. at the ends of the path of travel. This can be demonstrated by a simple calculation from which the acceleration is found to be 77 mm/sec?.

Since the total weight of the means subjected to the sinusoidal movement is 130 gr., with this weight taking into account part of the weight of the connecting member 13, the springs and the cables, the force of maximum acceleration (at the ends) is 102 gr. and varies linearly in relation to the path of travel x.

Byr giving the spring blades dimensions such that ,122204, the force of acceleration and the return force will balance one another at each point and thus ateach instant so that neither the connecting member, nor the eccentric, nor the shaft, nor its bearings are subjected to any appreciable effort in order to maintain a sinusoidal movement of the bar 1.

This can easily be understood if one considers that in the above condition, ythe oscillatory system would, during free oscillation, have the same movement as that imposed by the system made up of the connection member and eccentric and whose function, although essential, is simply to maintain strictly the amplitude, the frequency and the phase of the movement, despite the damping action of the air and of the hysteresis of the springs, and the physical differences between the theoretical values of the mass and of kthe elasticity of the system. The system composed of the connecting member and of the eccentric could of course be replaced by a simple electromagnetic maintenance and synchronization impulse.

The natural frequency of an oscillating system is l n f* 21T 'lf in which K is the constant of the elastic return force and M is mass. Since and as already noted) if the tracing is to remain xed on the paper during displacement of the writing head.

The curve A thus represents both the displacement and the voltage variation vx' during writing.

Every 20 ms. since the pitch is of 2.5 mm., a voltage jump of 2.5/s volts must occur. Moreover, this jump must occur in a direction opposite to its previous variation, so that an abrupt jump in voltage will take place in `a downward direction at the 20th, 40th and 60th ms. and in an upward direction at the th, 120th and 140th ms. At the same time, the change-over of the functions vx and vy of the previous tracing to the next tracing takes place. At the instants 0-80-160 ms., there is no jump of vx because at those instants a change in direction of the variation of vx', an abrupt jump of vy (curve C) and a change of line take place, consequently a change in the function vx and vy also takes place.

The voltage represented by curve B gives rise, added to the curve A,`to the curve A+B which is representative of the voltage vx applied permanently tothe electrodes x of the writing heads, in addition to the variable functions vx and vy.

All these voltages must be strictly synchronized with the oscillatory movement of the head and with the forward movement of the paper. It can thus be imagined that the shaft 15 carries the generator of the voltage represented by curve A and controls, for example magnetically or optically, the impulses for reversing the voltage represented by curve C. Since the speed of shaft 15, is moreover, synchronous with `the frequency of the input current of its motor, a purely electric synchronization can also be achieved. In the rst case, synchronization would ybe ensured independently of the rotary speed and the latter could therefore be subject to adjustment.

During the constanty periods of 20 rns. allotted to the writingo:` each character, the movements of the writing heads 4are obviously not constant ybecause of the sinusoidal law to which the movements are subjected; these displacements are respectively of 1.46, 3.54, 3.54 and 1.46 mm. at the instants A20, 40, 60 and 80 ms. during the forward movement, and follow one another in the same order during the next four steps of the return movement.

Thus, notwithstanding that the Writing heads cover different distances in equal times, the voltage vx' takes this into account and maintains the tracing stationary on the paper. This is `implicit in curves A, B and A+B, but the diagram of FIGURE 6, which is a plan representation of the relative and successive positions of one Writing head and of its four tracings, provides a geometric interpretation lthereof.

Referring to the time and motion diagram of FIGURE 6, during the rst 20 ms. period, the writing head E1 moves from 1i to 2i sinusoidally and travels 1.46 mm. The voltage vx must move the point of impact of tracing 1-2, which is located at 1.25 mm. away from the writing head axis for` purposes of symmetry, along x by the same distance of 1.46 mm. and according to the same sinusoidal law, i.e`. the voltage vx must have the point of impact in relation to the writing head axis from 1.25 to +0.21. The voltage vx will thus vary from At that instant, vx jumps from -I- to which amounts .to a variation of 3.54/s, and then jumps from i.e. by 2.5/s in all, and so forth in accordance with the diagram of FIGURE 6 and the curve A+B of FIG- URE 5.

At the instants -80-160 ms. occur the line changes caused by the jump of vy from 2 2 t s to s the spacing between the lines being 4 mm.; and since the speed of travel of the paper is constant, the variation of Vy' will `also be linear so as to immobilize the tracing in relation to the paper in the direction y.

In a modification fairly similar to the last described embodiment, there could be provided thirty writing heads which are fixed in relation to the frame of the machine.

Supposing that within the limits of its linear sensitivity, each writing head could project a tracing to a distance of 3.75 mm. on opposite sides of its `axis (see FIGURE 7), the voltage vx for a given head E, remains constant during the writing operation of each tracing l1, 2i, 3i, 41 as the head is fixed in relation to the paper in direction x and jumps abruptly by 2 5/s Volts every 20 ms. The function of vX and vy are changed over at the same time.

This method is applicable to the following three cases:

(a) Step-by-steptype-writer.

(b) Continuous outlet means in which the tracings of characters are made one after the other in the same chronological sequence as their logical sequence; and

(c) Ordinator outlet means in which all of the heads write out simultaneously the tracings on the same row in the order l, 2, 3, 4 and/ or reversely.

Case (a) The order of the four pairs of functions vx and vy per head per line is not known in advance, nor is the number of tracings per line. Consequently, the paper stationary (vy=0) andthe line spacing will be carried out by independent means, by the operator.

On the other hand, an automatic change-over must occur, upon each actuation of a key:

(l) Select the pair of functions vx, vy corresponding to the character tracing selected by the key.

(2) Select the writing head corresponding to the location of the group of four corresponding rows.

(3) Select the polarization vx corresponding to the appropriate row amongst the four which each fixed head comprises.

To summarize, the change-over automatically imposes the following sequence each time a key is actuated:

Ei, l, 2, 3, 4; Ei-I-l, l, 2, 3, 4, etc.

this same sequence being repeated for each head line.

Signal means, luminous or otherwise, indicate, in relation to the paper, the location of the next tracing during the next actuation of a key.

It is to be noted that in this case, the writing heads are stationary relatively to the paper during writing, so that the component vy is nil. There only remains the stepped component vX7-0.

Case (b) In this case, the length of the line is fixed in advance and the sequence of the character tracing is known and transmitted in logical order. Consequently, the paper Inay be moved forward at a constant speed and the polarization vy will be that represented by curve C in FIGURE 5. The sequence of fluid emissions per writing head per row is the same as in case (a) above. At the end of each line vy' jumps and simultaneously the cycle of emissions starts again at the beginning of each line. In this example, the only mechanical movement is the forward movement of the paper which takes place at constant speed.

Case (c) In this case, the ordination controls simultaneously the fluid emissions of all the writing heads, each head suc- 8 cessively emitting the four character tracings in the order l, 2, 3, 4.

The paper is moved forward at constant speed; the polarization vy is the same as in the preceding case, but at the end of each line, the writing of the following line can be done in the reverse direction; the order of emission of each head being then 4, 3, 2, 1. As in the preceding case, the only mechanical movement is the continuous mechanical forward movement of the paper at constant speed.

It should be noted that the emission of ink after any prolonged stoppage (say 15 seconds) cannot be started again immediately along the tracing of a character to be written in acceptable stability conditions. This is due to the fact that the ink meniscus which envelops the orifice of the writing head is in contact with the ambient air which causes a rapid change of the physical characteristics of the exposed layer (surface tension) owing to atmospheric contaminations and to the evaporation of the liquid carrier of the ink which causes a change in density of the latter. Thus, at the instant of starting, the optimum conditions of stability of the emission frequency and of focalization, in particular the precise value of the emission potential, are not achieved, and the jet is slightly dispersed, this dispersion being all the greater if the period of stoppage has been long. But this dispersion is rapidly reduced and disappears after a few milliseconds (l to 2 ms.).

The drawbacks due to this phenomenon can be overcome by associating with the writing head a starting target which is located outside the effective emission field, which is sufficiently large to cover the zone of dispersion, and at the centre of which is directed the jet by appropriate biasing of the dellecting plates during the l or 2 ms. which follow the starting of any emission after a stoppage of, for example, l0 seconds or more. The deflection of the jet from the target to the effective emission zone is done, without interrupting the emission, by an abrupt stoppage of the polarization voltage on the target. Indeed, the time required for this change-over can easily be reduced by means knownin the electronic art to below l its. and is therefore negligible in relation to the emission period (l/f, f=emission frequency ranging from 5 103 to 10X103 particles of ink per second) which is at least times longer so that there is at most one chance in a hundred for a single ink particle to be deposited on the path of travel from the target to the effective emission zone, and even in such a case, one particle of inkby itself remains invisible to the eye of the observer in relation to the actual tracing which comprises some two hundred uniformly deposited ink particles, assuming that the tracing takes 20 ms. to complete. Experience has confirmed this.

Nonetheless, continuous ink emission which is made possible by writing during relative movement between the Writing head and the paper constitutes an appreciable advantage by the suppression of the dead period of emission directed on to a target, by the suppression of the target and of the electronic circuits which enable polarization and temporization of the emission on to the target and by the neatness of the writing which is free of initial dispersion (as a matter of fact, the period of emission on to the target is determined by way of compromise with the tolerable dispersion during passage from the target to the effective emission zone). It is therefore clear that these advantages benefit only continuous writing methods and not a character-by-character writing method in which pauses can occur between characters.

It should be noted that the quantity of ink emitted per unit of time is constant. This has several consequences:

(a.) The time alloted to the writing of each character must be proportional to its blackened surface which is itself equal to the sum of the products of each component part of the length of the character tracing multiplied by the corresponding thickness of the line T=Kfledl Srfl edl (b) The thickness of the line is inversely proportional to the speed'at which the tracing is made. The possibility of writing in thick and thin seems evident.

(c) When writing characters constituted by lines of even thickness, the blackening is proportional to the time of emission on to the tracing which must always be travelled over at constant speed (according to b).

(d) For a given period of emission, a line having a certain thickness is obtained (blackening): it makes no diiterence whether the line be drawn in one stroke at a certain speed or in several strokes at a faster speed, although it is preferable to draw the line in one stroke at the slower speed because of the frequencies of the passing band of the voltages vX and vy.

(re) The ratio between the length of diierent letters or characters may vary greatly (1 to 5 for the Roman alphabet). Accordingly, if the tracing of each letter is to have a constant thickness, the `period of emission allotted to writing each letter will be proportional to the length of its tracing, this being implied in a).

This last requirement may appear to be in contradiction with the possibility of writing during movement in the case of a saw-toothed periodic voltage vx. In this case, the time T is the time available, but it is not necessary for this time to be fully utilized. Indeed T will be determined having regard to the longest tracing, since the period of emission for characters having a shorter tracing can be interrupted or the start of the emission can be delayed, by emitting on to the target, it being understood that in view of the method described this emission always occurs at the same place on the paper whatever may be the instant at which the emission starts and ends during the period T.

The period of dellection on to the target, the length of which varies for each character, may be a characteristic of each character in the same way as its own tracing and may be recorded in its memory.

While the invention has been described in certain preferred embodiments it is realized that moditications can be made, without departing from the'scope of the invention, and it is to be understood that no limitations upon the invention are intended other than those imposed by the scope ,of the appended claims.

I claim:

1. A method of writing on a recording surface which consists in discharging from a nozzle a jet of writing medium carrying electric charges across an atmospheric gap between the mouth of the nozzle and said surface, controlling the directional movement of the jet to trace characters on said surface by rst electric potentials with respect to at least two coordinated axes substantially parallel to the recording surface, effecting continuous relative movement beween said nozzle and said recordingy surface, and simultaneously correcting the directional movement of the jet by second electric potentials whose values represent at each instant the components, with respect to said axes, of the continuous relative movement between said surface and said nozzle whereby the characters may be traced Without deformation laterally of said recording surface despite said continuous relative movement.

2. A method as claimed in claim 1, wherein said second electric potentials are subjected, between two separate consecutive characters in a lateral line, to ak jump in a direction opposite their previous variation, said jump being made to occur at the instant when the writing of one character has been completed and before writing the next character, the value of `the potential jump being equal to the spacing between the two characters divided by the factor of sensitivity.

3. A writing machine comprising a platen for supporting a recording surface, a writing medium ydischarge nozzle directed Atowards said platen and spaced therefrom to form an atmospheric gap between the recording surface and the mouth of said nozzle, means for establishing an electric potential difference between the nozzle and the platen thereby to produce, durin operation, a jet of writing iiuid from said nozzle to said recording surface across said atmospheric gap, electric potentials means for controlling the directional movement of said jet with respect to at least two coordinated axes substantially parallel to the recording surface to trace characiers on said recording surface, means for effecting continuous relative movement between said nozzle and said platen, and means for producing additional electric potentials whose values represent at each instant the components, with respect to said axes, of said continuous relative movement thereby simultaneously to correct, during operation, the directional movement of the jet whereby the characters may be traced without deformation in a lateral line on said recording surface despite said continuous relative movement.

4. A machine as claimed in claim 3, wherein the means for eilecting continuous relative movement between said nozzle and said platen includes means for moving said platen at constant speed parallel to one of said axes, and wherein the corrective electric potential means include a saw-toothed potential generator.

5. A machine as claimed in claim 3, further comprising means for producing an electric potential of rectangular appearance intended to be added to the potentials produced by the corrective electric potential means to cause `a jump in potential between characters to separate said characters.

6. A machine as claimed in claim 3, comprising a plurality of nozzles and means for moving said platen at constant speed in a direction perpendicular to the lines of writing.

7. A machine as claimed in claim 6, comprising a support in which said nozzles are equidistantly mounted, said relative movement means including means for imparting to said support an oscillatory movement having an amplitude substantially equal to the distance between two adjacent nozzles.

8. A machine as claimed in claim 6, comprising a support on which said nozzles are equidistantly supported, and spring means on which said support is mounted, said relative movement means including means for imparting to said support oscillations having an amplitude substantially equal to the distance between two adjacent nozzles and a frequency substantially equal to the natural frequency of oscillation of the support on said springs.

References Cited in the le of this patent UNITED STATES PATENTS 2,577,894 Jacob Dec. 11, 1951 2,600,129 Richards .lune 10, 1952 2,628,881 Adams Feb. 17, 1953 2,894,799 McCreary July 14, 1959 2,925,312 Hollmann Feb. 16, 1960 3,004,819 Anderson Oct. 17, 1961 3,023,070 Benn Feb. 27, 1962 3,048,846 Martin Aug. 7, 1962 3,050,731 U'sdin Aug. 21, 1,962 3,060,429 Winston Oct. 23, 1962 3,063,050 Millis Nov. 6, 1962 

1. A METHOD OF WRITING ON A RECORDING SURFACE WHICH CONSISTS IN DISCHARGING FROM A NOZZLE A JET OF WRITING MEDIUM CARRYING ELECTRIC CHARGES ACROSS AN ATMOSPHERIC GAP BETWEEN THE MOUTH OF THE NOZZLE AND SAID SURFACE, CONTROLLING THE DIRECTIONAL MOVEMENT OF THE JET TO TRACE CHARACTERS ON SAID SURFACE BY FIRST ELECTRIC POTENTIALS WITH RESPECT TO AT LEAST TWO COORDINATED AXES SUBSTANTIALLY PARALLEL TO THE RECORDING SURFACE, EFFECTING CONTINUOUS RELATIVE MOVEMENT BETWEEN SAID NOZZLE AND SAID RECORDING 